It is common practice in the automated handling of mail documents, such as mailing envelopes and flats, to progressively feed a stack of documents from a feeder station or feeder station magazine to a shingling station and then to a singulating station. The shingling station functions to partially separate the stack of mail into an overlapping stream. The singulating station completes the process of separating individual items of mail from the overlapping stack. The separated documents are then directed from the singulating stations to sorting stations or other processing stations or devices.
Postal requirements demand that a high volume of documents be handled in a short period of time. Typically, document handling devices are required to process thousands of documents per hour with a minimum of sorting defects and product damage. Often documents of varying sizes and shapes from a number of handling stations must be merged seamlessly into sorting processes.
Typically, the first stage in the document handling process after the documents have been placed in a container or tray with the labels facing the same direction, is to load the stack of documents onto a transport mechanism, such as a conveyor belt mechanism. The transport mechanism then directs the documents into the various separators and sorting devices.
Known systems and methods typically require substantial human intervention and action to load the stacks of documents from the tray or containers onto the document transport mechanism. The operator must gather the stacks of documents and place the documents on the conveyor belt so that all the documents are in an on-edge orientation. This must be performed while taking steps to prevent the stack from falling over. Additionally, these steps are typically performed as the conveyor belt is continuously advancing the stack of documents toward the various processing stations. This is a time-intensive process and is often one of the limiting factors in achieving high-speed document processing and throughput.
The documents are typically transported to an initial processing station, such as a shingling station, prior to singulation. Shingling results in orienting either the top or bottom document in a vertical stack, or the front or lead document in an on-edge stack, so that the forward or leading edge of each successive top, bottom or front document is disposed slightly forward or laterally of the leading edge of the next adjacent document. By shingling the stacked documents, only one document at a time will enter a nip defined by singulating belts or rollers, thereby substantially reducing the possibility that more than one document at a time will be fed simultaneously through the singulating belts or rollers. The singulating belts or rollers then transport each document in an on-edge single file manner toward other sorting and processing devices.
The other sorting and processing devices are often fed from a sorting conveyor which also operates in an on-edge orientation. The sorting conveyor is often constructed of fingered belts in which a set of projecting fingers spaced at pre-determined horizontal intervals along the belt define spaces for individual documents (i.e., designated document locations). The fingers both define the spaces and function to urge the documents along the sorting conveyor to the individual sorting stations.
As the documents move along the sorting conveyor, a zip code or other indicia of destination is read from the documents. At the sorting station, the documents found between the fingers of the sorting conveyor are discharged, either pneumatically or by actuator levers, into predetermined receiving bins.
To perform their designated function, the singulating stations must discharge the singulated documents onto the sorting conveyor between the fingers of the sorting conveyor. To place the documents between the fingers of the sorting conveyors, the singulating stations must be synchronized to the movement of the fingers of the sorting conveyor. Often this requires detecting a position of an envelope and adjusting a processing speed of the singulating station to match that of the sorting conveyor. Optical sensors may be used to detect either the lead or trail edge of the mail piece so that software can adjust the speed and relative position of the output documents of the singulating station to match the finger location of the sorting conveyor.
Because of the difficulty of loading and maintaining a constant flow of documents through the singulating stations, the sorting conveyors are often fed from a number of singulating stations. Where a number of singulating stations feed the same sorting conveyor, it is often difficult to coordinate and synchronize placement of the documents into the designated document locations. A means must be provided to avoid placing two envelopes from different feeders into the same location. Where an envelope overlaps a boundary of the designated location (e.g, a finger of the fingered belt), it becomes necessary to determine whether the envelope belongs in the prior location or subsequent location. Thus a means and apparatus for reliably synchronizing document placement into the sorting conveyor would greatly improve the rate at which documents could be handled in a mail processing system.
Accordingly, it is an object of the invention to provide a means and apparatus for precisely synchronizing the output of the singulating stations to the sorting conveyor.
It is a further object to provide a means and apparatus to synchronize the individual documents of an output of the singulating station to the fingers of the sorting conveyor, instead of synchronizing the entire singulating station.